Automatic gopath selection, and godoc web server execution with zshell

.zshrc

# List Custom gopaths
gopaths=('/home/piers/projects/ethdenver' '/home/piers/projects/test_gopath')

# Always available gopath
fallback_gopath=$HOME/go
# Used to detect when the gopath changes
previous_gopath=''

#setgopath sets the gopath based on the current working dierectory. If the
#current working dierectory is a gopath or a subdirectory of a gopath then
#export that gopath, otherwise choose the first gopath as the default gopath
#and export that. This allows for shell navigation through many gopaths without
#having manually set the gopath.
function setgopath() {
	# Remove bin paths from PATH
	binpath=:$fallback_gopath/bin
	export PATH="${PATH/$binpath/}"

	if [[ ! -z $previous_gopath ]]; then
		binpath=:$previous_gopath/bin
		# ${X/Y/Z} Replace first occurrence of Y in X with Z.
		export PATH="${PATH/$binpath/}"
	fi

	# Set current_path
	current_path=`pwd`
	# Set empty current_gopath.
	current_gopath=''

	for p in $gopaths; do
		# if we are in a gopath then set the current_gopath. 
		if [[ $current_path == $p* ]]; then
			current_gopath=$p
			break
		fi
	done

	unset GOPATH

	if [[ ! -z $current_gopath ]]; then
		export GOPATH="$current_gopath:$fallback_gopath"
		export PATH="$PATH:$current_gopath/bin:$fallback_gopath/bin"
	else
		export GOPATH="$fallback_gopath"
		export PATH="$PATH:$fallback_gopath/bin"
	fi

	# Restart godoc server if path has changed
	if [[ $current_gopath != $previous_gopath ]]; then
		# restart godoc server
		killall godoc &> /dev/null
		&> /dev/null (godoc -http=:6060 &)	
	fi

	previous_gopath=$current_gopath
}

# Upadte the prompt with the time taken from the timer.
function precmd() {
	# set the gopath based on our current path.
	setgopath
}