This program download all attachements files to a discord message and save it only if it's not already saved.
How it work
Files are downloaded in the directory under the SRC_DIR environment variable and are named with an UUID.
The bot look for his connection token in the environment variable named TKN.
A goroutine watch files in the directory under the SRC_DIR environment variable and check if the file is in the directory DST_DIR
environment variable.
If a file from the SRC_DIR is already present in the DST_DIR it's removed, otherwise the file is moved.