Go http get crashes on retrieving high-latency resources -
i have panicking program intends illustrate issue of retrieving high-latency resources via golang's http client.
does have clue why happening?
go version go1.5.1 linux/amd64
package main import ("fmt" "net/http" "time" "net") func main() { i:=0; i<2000; i++ { start := time.now() client := &http.client{} // enough program crash /*client := &http.client{ transport: &http.transport{ dial: (&net.dialer{ timeout: 1 * time.second, keepalive: 0, }).dial, disablekeepalives: true, disablecompression: true, maxidleconnsperhost: 1, responseheadertimeout: 1*time.second, }, }*/ req, _ := http.newrequest("get", "http://mickle.com.au/wp-content/uploads/2015/03/11222.jpg", nil) req.header.add("connection", "close") req.header.add("accept-encoding", "none") response, _ := client.do(req) fmt.printf("httpreq took %s. resp status: %s\n", time.since(start), response.status) response.body.close() } } http://play.golang.org/p/nmnfb_x2yu
httpreq took 817.750359ms. resp status: 200 ok httpreq took 798.177493ms. resp status: 200 ok [[... left out 33 lines...]] httpreq took 795.433486ms. resp status: 200 ok httpreq took 805.610082ms. resp status: 200 ok panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x0 pc=0x4014a6] goroutine 1 [running]: main.main() /home/bongo/downloads/a.go:32 +0x4a6 goroutine 17 [syscall, locked thread]: runtime.goexit() /usr/lib/golang/src/runtime/asm_amd64.s:1696 +0x1 goroutine 8 [select]: net/http.(*persistconn).readloop(0xc8200ac000) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 9 [select]: net/http.(*persistconn).writeloop(0xc8200ac000) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 40 [select]: net/http.(*persistconn).readloop(0xc8200ac2c0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 76 [select]: net/http.(*persistconn).readloop(0xc8200e22c0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 34 [select]: net/http.(*persistconn).readloop(0xc8200e2000) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 35 [select]: net/http.(*persistconn).writeloop(0xc8200e2000) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 12 [select]: net/http.(*persistconn).readloop(0xc8200ac0b0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 13 [select]: net/http.(*persistconn).writeloop(0xc8200ac0b0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 16 [select]: net/http.(*persistconn).readloop(0xc8200ac160) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 50 [select]: net/http.(*persistconn).writeloop(0xc8200ac160) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 38 [select]: net/http.(*persistconn).readloop(0xc82010e000) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 39 [select]: net/http.(*persistconn).writeloop(0xc82010e000) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 53 [select]: net/http.(*persistconn).readloop(0xc8200ac210) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 54 [select]: net/http.(*persistconn).writeloop(0xc8200ac210) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 61 [select]: net/http.(*persistconn).readloop(0xc8200e2160) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 41 [select]: net/http.(*persistconn).writeloop(0xc8200ac2c0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 44 [select]: net/http.(*persistconn).readloop(0xc82010e0b0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 45 [select]: net/http.(*persistconn).writeloop(0xc82010e0b0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 59 [select]: net/http.(*persistconn).readloop(0xc8200ac370) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 60 [select]: net/http.(*persistconn).writeloop(0xc8200ac370) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 22 [select]: net/http.(*persistconn).readloop(0xc8200e20b0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 23 [select]: net/http.(*persistconn).writeloop(0xc8200e20b0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 78 [select]: net/http.(*persistconn).readloop(0xc8200e2370) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 62 [select]: net/http.(*persistconn).writeloop(0xc8200e2160) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 48 [select]: net/http.(*persistconn).readloop(0xc82010e160) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 49 [select]: net/http.(*persistconn).writeloop(0xc82010e160) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 28 [select]: net/http.(*persistconn).readloop(0xc8200e2210) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 29 [select]: net/http.(*persistconn).writeloop(0xc8200e2210) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 70 [select]: net/http.(*persistconn).readloop(0xc8200ac420) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 68 [select]: net/http.(*persistconn).readloop(0xc820170000) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 69 [select]: net/http.(*persistconn).writeloop(0xc820170000) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 101 [select]: net/http.(*persistconn).readloop(0xc8201702c0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 71 [select]: net/http.(*persistconn).writeloop(0xc8200ac420) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 74 [select]: net/http.(*persistconn).readloop(0xc8201700b0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 75 [select]: net/http.(*persistconn).writeloop(0xc8201700b0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 84 [select]: net/http.(*persistconn).readloop(0xc82010e210) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 85 [select]: net/http.(*persistconn).writeloop(0xc82010e210) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 99 [select]: net/http.(*persistconn).readloop(0xc8200ac4d0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 100 [select]: net/http.(*persistconn).writeloop(0xc8200ac4d0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 88 [select]: net/http.(*persistconn).readloop(0xc82010e2c0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 89 [select]: net/http.(*persistconn).writeloop(0xc82010e2c0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 80 [select]: net/http.(*persistconn).readloop(0xc82010e370) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 77 [select]: net/http.(*persistconn).writeloop(0xc8200e22c0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 122 [select]: net/http.(*persistconn).readloop(0xc820170160) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 79 [select]: net/http.(*persistconn).writeloop(0xc8200e2370) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 116 [select]: net/http.(*persistconn).readloop(0xc8200e2420) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 117 [select]: net/http.(*persistconn).writeloop(0xc8200e2420) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 120 [select]: net/http.(*persistconn).readloop(0xc8200e24d0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 121 [select]: net/http.(*persistconn).writeloop(0xc8200e24d0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 81 [select]: net/http.(*persistconn).writeloop(0xc82010e370) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 147 [select]: net/http.(*persistconn).readloop(0xc8200e2580) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 123 [select]: net/http.(*persistconn).writeloop(0xc820170160) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 134 [select]: net/http.(*persistconn).readloop(0xc820170210) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 135 [select]: net/http.(*persistconn).writeloop(0xc820170210) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 178 [select]: net/http.(*persistconn).readloop(0xc82010e580) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 102 [select]: net/http.(*persistconn).writeloop(0xc8201702c0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 105 [select]: net/http.(*persistconn).readloop(0xc8200ac580) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 106 [select]: net/http.(*persistconn).writeloop(0xc8200ac580) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 109 [select]: net/http.(*persistconn).readloop(0xc8200ac630) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 110 [select]: net/http.(*persistconn).writeloop(0xc8200ac630) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 113 [select]: net/http.(*persistconn).readloop(0xc8200ac6e0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 146 [select]: net/http.(*persistconn).writeloop(0xc8200ac6e0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 140 [select]: net/http.(*persistconn).readloop(0xc820170370) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 141 [select]: net/http.(*persistconn).writeloop(0xc820170370) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 144 [select]: net/http.(*persistconn).readloop(0xc820170420) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 145 [select]: net/http.(*persistconn).writeloop(0xc820170420) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 94 [select]: net/http.(*persistconn).readloop(0xc82010e420) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 95 [select]: net/http.(*persistconn).writeloop(0xc82010e420) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 162 [select]: net/http.(*persistconn).readloop(0xc82010e4d0) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 163 [select]: net/http.(*persistconn).writeloop(0xc82010e4d0) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 179 [select]: net/http.(*persistconn).writeloop(0xc82010e580) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 126 [select]: net/http.(*persistconn).readloop(0xc82010e630) /usr/lib/golang/src/net/http/transport.go:976 +0xac7 created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:685 +0xc78 goroutine 148 [select]: net/http.(*persistconn).writeloop(0xc8200e2580) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d goroutine 127 [select]: net/http.(*persistconn).writeloop(0xc82010e630) /usr/lib/golang/src/net/http/transport.go:1009 +0x40c created net/http.(*transport).dialconn /usr/lib/golang/src/net/http/transport.go:686 +0xc9d exit status 2
the request getting error you're ignoring , nil pointer dereference when attempt access response status in printf on next line.
here example printing error; http://play.golang.org/p/v8bcrm_ag7
every request gets this; http://mickle.com.au/wp-content/uploads/2015/03/11222.jpg: dial tcp: protocol not available
basically, need assign error , check before allow execution continue. common syntax this;
if response, err := client.do(req); err != nil { // handles error , return } 
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