Add dynamic GOROOT setting for zsh (#56)

Co-authored-by: Kenny Parnell <k.parnell@gmail.com>

README.md

@@ -25,6 +25,13 @@ asdf plugin-add golang https://github.com/kennyp/asdf-golang.git
 
 Check the [asdf](https://github.com/asdf-vm/asdf) readme for instructions on how to install & manage versions of go.
 
+## `GOROOT`
+
+To set `GOROOT` in your shell's initialization add the following:
+
+**zsh shell**  
+`. ~/.asdf/plugins/golang/set-env.zsh`  
+
 ## When using `go get` or `go install`
 
 After using `go get` or `go install` to install a package you need to run `asdf reshim golang` to get any new shims.

set-env.zsh

@@ -0,0 +1,17 @@
+function absolute_dir_path {
+    local absolute_path
+    absolute_path="$( cd -P "$( dirname "$1" )" && pwd )"
+    echo "$absolute_path"
+}
+
+asdf_update_golang_env() {
+  local go_path
+  go_path="$(asdf which go)"
+  if [[ -n "${go_path}" ]]; then
+    export GOROOT
+    GOROOT="$(dirname "$(absolute_dir_path "${go_path}")")"   
+  fi
+}
+
+autoload -U add-zsh-hook
+add-zsh-hook precmd asdf_update_golang_env