residentsleeper is a TUI API client created as a clone of Insomnia, so I can get experience developing Go/Bubbletea. It also comes with a mock server you can use to test it.

After cloning the repo, you can run residentsleeper using go run main.go from the main repo folder. You can additionally run go run server/main.go in a separate tab to run the bundled mock server.

You'll probably need to resize the window to be bigger - I've been fixing a few funky things with UI in the default terminal window size, but parts of the UI might get cut off otherwise. Unfortunately, I don't know of any way to set the terminal width/height in bubbletea or I'd do that.
I've also provided a few queries you can use with the mock server to demo the client's functionality.

When creating a header or query parameter, it should be in a name:value format. Anything that doesn't follow that format will not be saved after editing it.