What version of Go are you using (go version)?

go version go1.7.4 linux/amd64

What operating system and processor architecture are you using (go env)?

actually it's Manjaro

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/bruce/go_ext_path"
GORACE=""
GOROOT="/usr/lib/go"
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build134643851=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

What did you do?

git config --global http.proxy 'socks5://127.0.0.1:1080'
git config --global https.proxy 'socks5://127.0.0.1:1080'
export http_proxy=socks5://127.0.0.1:1080
export https_proxy=socks5://127.0.0.1:1080
go get -u -v github.com/zmb3/gogetdoc

What did you expect to see?

Git can use socks5 proxy to clone a repo, so i expect go get can use socks5 proxy to download/update package github.com/zmb3/gogetdoc

What did you see instead?

github.com/zmb3/gogetdoc (download)
Fetching https://golang.org/x/tools/go/buildutil?go-get=1
https fetch failed: Get https://golang.org/x/tools/go/buildutil?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout
package golang.org/x/tools/go/buildutil: unrecognized import path "golang.org/x/tools/go/buildutil" (https fetch: Get https://golang.org/x/tools/go/buildutil?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout)
Fetching https://golang.org/x/tools/go/loader?go-get=1
https fetch failed: Get https://golang.org/x/tools/go/loader?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout
package golang.org/x/tools/go/loader: unrecognized import path "golang.org/x/tools/go/loader" (https fetch: Get https://golang.org/x/tools/go/loader?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout)
[bruce@bruce-manjaro ~]$ set https_proxy=socks5://127.0.0.1:1080
[bruce@bruce-manjaro ~]$ go get -u -v github.com/zmb3/gogetdoc
github.com/zmb3/gogetdoc (download)
Fetching https://golang.org/x/tools/go/buildutil?go-get=1
https fetch failed: Get https://golang.org/x/tools/go/buildutil?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout
package golang.org/x/tools/go/buildutil: unrecognized import path "golang.org/x/tools/go/buildutil" (https fetch: Get https://golang.org/x/tools/go/buildutil?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout)
Fetching https://golang.org/x/tools/go/loader?go-get=1
https fetch failed: Get https://golang.org/x/tools/go/loader?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout
package golang.org/x/tools/go/loader: unrecognized import path "golang.org/x/tools/go/loader" (https fetch: Get https://golang.org/x/tools/go/loader?go-get=1: http: error connecting to proxy http://socks5://127.0.0.1:1080: dial tcp 59.50.43.82:0: i/o timeout)