check for go binary in ci builds (#6570)

build-support/functions/00-vars.sh

@@ -9,6 +9,7 @@ GO_BUILD_CONTAINER_DEFAULT="consul-build-go"
 COLORIZE=${COLORIZE-1}
 
 # determine GOPATH and the first GOPATH to use for intalling binaries
+if command -v go >/dev/null; then
    GOPATH=${GOPATH:-$(go env GOPATH)}
    case $(uname) in
          CYGWIN*)
@@ -16,6 +17,7 @@ case $(uname) in
             ;;
    esac
    MAIN_GOPATH=$(cut -d: -f1 <<< "${GOPATH}")
+fi
 
 # Build debugging output is off by default
 BUILD_DEBUG=${BUILD_DEBUG-0}