Go Language - Parse OS environment variables and expand values in template

This parse_env.go read all your environment variables to the map (hash table).

And also expand variable values in string template.

Example

input := `
Hello world, my home dir is {HOME} and logname is {LOGNAME}. 
My terminal type is {TERM}
`

Result is:

Hello world, my home dir is /home/myusername and logname is myusername.
My terminal type is xterm-256

	// envvars map (hash table) include variable values
	// regexp rule to find {XXX} strings

	input := 'some text including {TERM} variables to expand like HOME:{HOME}`
        r := regexp.MustCompile(`{([^}]+)}`)
        result := Expand(input,r,envvars)