build.sh: supporting go1.9 and above

Author: Shlomi Noach

build.sh

@@ -10,7 +10,7 @@ function build {
     GOOS=$3
     GOARCH=$4
 
-    if [[ $(go version | egrep "go1[.][012345678]") ]]; then
+    if ! go version | egrep -q 'go(1[.]9|1[.]1[0-9])' ; then
       echo "go version is too low. Must use 1.9 or above"
       exit 1
     fi