lock-catcher.js

// node lock-catcher.js myprogram.go

var reader = require('line-reader')
var file = process.argv[2]

var prev = null
reader.eachLine(file, function (line) {
  if (prev && /Lock/.test(prev) && !/defer/.test(line)) {
    console.error('You probably messed up.')
  }
  prev = line
})