Optionally add GOPATH/bin || GOBIN to PATH env variable

[Mzack9999]

Please describe your feature request:

The $GOPATH/bin path not present in $PATH environment variable and the subsequent binary not found error is a common scenario for everyone installing any go tool. We should consider adding it as last one along with pdtm one, so that the final PATH env variable looks like this:

export PATH=$PATH:$HOME/.pdtm/bin:$GOPATH/bin

Notes:

• Maybe the behavior should be optional, but it would automatically make life easier for countless people just starting with go and not familiar with dozen of shells configuration files
• The GOPATH might be scoped only to the go binary, so it should be retrieved via go env GOPATH output
• If GOBIN is defined, it has priority over GOPATH/bin

[gedw99]

This is a really good idea.