Address review comments

1. Removed the check_go_version script
2. Only check go version in bootstrap
3. Simplify the go version check logic

script/bootstrap

@@ -1,6 +1,5 @@
 #!/usr/bin/env bash
 set -e
-source script/check_go_version
 
 STATUS=0
 
@@ -17,7 +16,11 @@ if [ -n "$TRAVIS" ] && [ ! -x ~/bin/tmux ]; then
   curl -fsSL "https://${AMAZON_S3_BUCKET}.s3.amazonaws.com/${cache_name}.tgz" | tar -xz -C ~
 fi
 
-check_go_version
+go_ver="$(go version | grep -o '1.[[:digit:]]\+' | head -1)"
+if [ "${go_ver#*.}" -lt 8 ]; then
+  echo "You need to install Go 1.8 or higher to build hub" >&2
+  STATUS=1
+fi
 
 { ruby --version
   if [ -n "$TRAVIS" ]; then

script/build

@@ -8,9 +8,6 @@
 # With `test`, runs tests instead.
 
 set -e
-source script/check_go_version
-
-check_go_version
 
 windows=
 [[ $OS == Windows* ]] && windows=1

script/check_go_version

@@ -1,41 +0,0 @@
-#!/usr/bin/env bash
-
-# This script is only used by importing into other scripts.
-GO_VERSION_REGEX="go(1\.[89]|[2-9]\.[0-9]{1,}|[0-9]{2,}\.[0-9]{1,})(\.[0-9]{1,})?[[:space:]]"
-
-check_go_version() {
-  if ! go version | grep -E $GO_VERSION_REGEX &> /dev/null; then
-    echo "You need to install Go 1.8 or higher to build hub" >&2
-    exit 1
-  else
-    go version
-  fi
-}
-
-test_go_version() {
-  if ! echo $1 | grep -E $GO_VERSION_REGEX &> /dev/null; then
-    echo "FAIL $1" >&2
-  else
-    echo "PASS $1"
-  fi
-}
-
-test_go_versions() {
-  test_go_version "go version go0.1 darwin/amd64"
-  test_go_version "go version go0.2 darwin/amd64"
-  test_go_version "go version go1.6 darwin/amd64"
-  test_go_version "go version go1.7.8 darwin/amd64"
-  test_go_version "go version go1.8 darwin/amd64"
-  test_go_version "go version go1.8.1 darwin/amd64"
-  test_go_version "go version go1.8.10 darwin/amd64"
-  test_go_version "go version go1.9 darwin/amd64"
-  test_go_version "go version go2.0 darwin/amd64"
-  test_go_version "go version go2.0.1 darwin/amd64"
-  test_go_version "go version go3.1 darwin/amd64"
-  test_go_version "go version go4.5 darwin/amd64"
-  test_go_version "go version go5.6 darwin/amd64"
-  test_go_version "go version go6.7 darwin/amd64"
-  test_go_version "go version go10.1 darwin/amd64"
-  test_go_version "go version go10.1 darwin/amd64"
-  test_go_version "go version go10.10.10 darwin/amd64"
-}