_golang: switch listing of GOPATH/GOROOT with _call_program (suggestion by @okapia)

Author: pseyfert

src/_golang

@@ -48,11 +48,11 @@
 #
 #   * To disable listing packages from GOROOT (i.e. Go stdlib) in completions use:
 #
-#       zstyle ':completion:*:go:*' no-goroot true
+#       zstyle ':completion:*:go-packages-goroot' command ""
 #
 #   * To disable listing packages from GOPATH in completions use:
 #
-#       zstyle ':completion:*:go:*' no-gopath true
+#       zstyle ':completion:*:go-packages-gopath' command ""
 #
 # ------------------------------------------------------------------------------
 
@@ -370,12 +370,9 @@ case $state in
     __go_packages() {
       local gopaths
       declare -a gopaths
-      if ! zstyle -t ":completion:${curcontext}:" no-gopath; then
-        gopaths=("${(s/:/)$(go env GOPATH)}")
-      fi
-      if ! zstyle -t ":completion:${curcontext}:" no-goroot; then
-        gopaths+=("$(go env GOROOT)")
-      fi
+      gopaths=()
+      gopaths+=("${(s/:/)$(_call_program go-packages-gopath go env GOPATH)}")
+      gopaths+=("${(s/:/)$(_call_program go-packages-goroot go env GOROOT)}")
       for p in $gopaths; do
         _path_files $@ -W "$p/src" -/
       done