code: func LoadECDSA(file string) (*ecdsa.PrivateKey, error) {
  	buf := make([]byte, 64)
  	fd, err := os.Open(file)
  	if err != nil {
  		return nil, err
  	}
  	defer fd.Close()
  	if _, err := io.ReadFull(fd, buf); err != nil {
  		return nil, err
  	}
  
  	key, err := hex.DecodeString(string(buf))
  	if err != nil {
  		return nil, err
  	}
  	return ToECDSA(key)
  }
docs: // LoadECDSA loads a secp256k1 private key from the given file.