It's really useful to have access to an eval() function when paused in a debugger. That alone makes this useful -- it'd be great to have IDE's like Goland take advantage of this to provide this functionality.
It must be some subset of expressions (or I must have set mine up wrong), because anything that calls a function (vs a simple conditional statement) appears to throw an error for me indicating that it cannot execute.
https://www.jetbrains.com/help/go/debugging-code.html#924cf9...