$ go run main.go -h
Usage: base64 [-h] <file_name>
-h, --help display this message
$ make build
# Encode
$ cat test.txt
ab%
$ ./base64 test.txt
YWI=
# Decode
$ ./base64 test.txt > encoded_test.txt
$ ./base64 -d encoded_test.txt
ab%
$ make build
# Encode
$ cat test.txt | ./base64
YWI=
# Decode
$ ./base64 test.txt > encoded_test.txt
$ cat encoded_test.txt| ./base64 -d
ab%
$ at test.txt | ./base64 | ./base64 -d
ab%
under MIT License.