promise wrapper around crypto.createHash

hash.js

const crypto = require('crypto')

module.exports = function hash({ method }, input) {
  return new Promise((res, rej) => {
    const h = crypto.createHash(method)
    h.on('readable', () => {
      const data = h.read()
      if (data) {
        res(data.toString('hex'))
      } else rej()
    })
    h.write(input)
    h.end()
  })
}