feat(goenv): adding new plugin for 'goenv'

plugins/goenv/README.md

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+# goenv
+
+This plugin looks for [goenv](https://github.com/syndbg/goenv), a Simple Go-lang version
+management system, and loads it if it's found.
+
+To use it, add `goenv` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... goenv)
+```
+
+## Functions
+
+- `goenv_prompt_info`: displays the Go-lang version in use by goenv; or the global Go-lang
+  version, if goenv wasn't found.

plugins/goenv/goenv.plugin.zsh

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+# This plugin loads goenv into the current shell.
+
+# Load goenv only if command not already available
+if command -v goenv &> /dev/null && [[ "$(uname -r)" != *icrosoft* ]]; then
+  FOUND_GOENV=1
+else
+  FOUND_GOENV=0
+fi
+
+if [[ $FOUND_GOENV -ne 1 ]]; then
+  goenvdirs=("$HOME/.goenv" "/usr/local/goenv" "/opt/goenv" "/usr/local/opt/goenv")
+  for dir in $goenvdirs; do
+    if [[ -d $dir/bin ]]; then
+      export PATH="$PATH:$dir/bin"
+      FOUND_GOENV=1
+      break
+    fi
+  done
+fi
+
+if [[ $FOUND_GOENV -ne 1 ]]; then
+  if (( $+commands[brew] )) && dir=$(brew --prefix goenv 2>/dev/null); then
+    if [[ -d $dir/bin ]]; then
+      export PATH="$PATH:$dir/bin"
+      FOUND_GOENV=1
+    fi
+  fi
+fi
+
+if [[ $FOUND_GOENV -eq 1 ]]; then
+  eval "$(goenv init -)"
+  function goenv_prompt_info() {
+    echo "$(goenv version-name)"
+  }
+else
+  # fallback to system python
+  function goenv_prompt_info() {
+    echo "system: $(go verson 2>&1 | cut -f 3 -d ' ')"
+  }
+fi
+
+unset FOUND_GOENV goenvdirs dir