title: go get fails with unrecognized import path after upgrading to go 1.10
body: <p><strong>Before setting proxy:</strong></p>
  
  <p><code>$ go get -u google.golang.org/grpc</code></p>
  
  <pre><code>package google.golang.org/grpc: unrecognized import path "google.golang.org/grpc" (https fetch: Get https://google.golang.org/grpc?go-get=1: dial TCP 172.217.160.145:443: connected: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)
  </code></pre>
  
  <p><strong>After setting proxy:</strong></p>
  
  <p><code>$ go get -u google.golang.org/grpc</code></p>
  
  <pre><code>package google.golang.org/grpc: unrecognized import path "google.golang.org/grpc" (https fetch: Get https://google.golang.org/grpc?go-get=1: proxyconnect tcp: EOF)
  </code></pre>
  
  <p>I have tried every solution I could find on StackOverflow. I am still not able to solve this issue. </p>
  
  <p><code>$ go env</code></p>
  
  <pre><code>$ go env
  set GOARCH=amd64
  set GOBIN=
  set GOCACHE=C:\Users\gayr\AppData\Local\go-build
  set GOEXE=.exe
  set GOHOSTARCH=amd64
  set GOHOSTOS=windows
  set GOOS=windows
  set GOPATH=C:\Users\gayr\GolandProjects
  set GORACE=
  set GOROOT=C:\Go
  set GOTMPDIR=
  set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
  set GCCGO=gccgo
  set CC=gcc
  set CXX=g++
  set CGO_ENABLED=1
  set CGO_CFLAGS=-g -O2
  set CGO_CPPFLAGS=
  set CGO_CXXFLAGS=-g -O2
  set CGO_FFLAGS=-g -O2
  set CGO_LDFLAGS=-g -O2
  set PKG_CONFIG=pkg-config
  set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\gayr\AppData\Local\Temp\go-build135172366=/tmp/go-build -gno-record-gcc-switches
  </code></pre>
  
  <p>How can I resolve this?</p>