Empty service definition in proto file produces bad go code

[ofpiyush]

Steps to reproduce:

Try compiling this

syntax = "proto3";
package foo;
service Bar {
}

Errors:

imported and not used: "strings"
prefix declared and not used

Fixes:

Add a method to prevent import failing right after import statements

var _ = strings.Index

// Add empty use to prevent prefix failing in client functions

_ = prefix

[spenczar]

Thanks for the bug report. I'll put together a fix and a release.

[spenczar]

Fixed in #172, release v5.7.0.