Launch the app, then go into preferences, security and allow the app to be executed, since it is not trusted by Apple.
To make the app run at startup open preferences, users, [your user], login items and add the app to the list
Linux
Download the latest release for Linux (the simple drink_linux binary file) and place it wherever you want
To make the app runnable from the applications grid, first launch it from the terminal, then you need to create water-reminder.desktop file in $HOME/.local/share/applications and copy this, changing [your username]
[Desktop Entry]
Name=Water Reminder
Exec=/path/to/drink_linux
Terminal=false
Type=Application
Comment=Remember to drink every 30 minutes
Icon=/home/[your username]/.config/water-reminder/water-glass.png
To make the app run at startup (using water-reminder.desktop and if you have gnome-tweak-tools installed) you can open Tweaks and add Water Reminder to the startup applications. Otherwise, if you didn't create water-reminder.desktop or if you don't have gnome-tweak-tools, open "Startup Applications", press "Add" and in the command section type path/to/drink_linux. Give the app the name you want
Build
To build from source, all you need to do is to install Go (the latest version is ok), clone the repo (go.mod and go.sum files (Go modules) will install for you every Go library needed) and then build with go build -o [name] drink.go lib.go