code: async function Multihashing (buf, alg, length) {
    const digest = await Multihashing.digest(buf, alg, length)
    return multihash.encode(digest, alg, length)
  }
docs: Hash the given `buf` using the algorithm specified by `alg`.
  @param {Buffer} buf - The value to hash.
  @param {number|string} alg - The algorithm to use eg 'sha1'
  @param {number} [length] - Optionally trim the result to this length.
  @returns {Promise<Buffer>}