proposal: runtime: add a function to install a global go-routine panic handler

[markusheukelom]

package runtime

// Recover installs a handler function that is called whenever a panicking sequence
// in any Go routine is not stopped by a call to recover in a locally deferred function call. 
//
// If no handler function is installed the program aborts.
//
// By default, no handler function is installed.
// 
// The handler function runs as if a defer-recover preamble was added to the function on 
// which the `go` operatorr is invoked:
//  
//     defer func() { if r := recover(); r != nil { handler(r) } }
//
// This means that, for example, the stack of the panicking go-routine can be retrieved use `debug.Stack`, etc.
func Recover(handler func(r any)) {}

[mvdan]

Please note that you should fill https://github.com/golang/proposal/blob/master/go2-language-changes.md when proposing a language change. I realise that this is technically not a language change, but this is still a substantial change to how recover works in practice, which is a part of the language.

[wizardishungry]

Why not introduce a function that lets you override go itself:

func Go(handler func(
  goF func(func()),
  f func() ,
))

Calls to go f() will be passed to handler with a goF argument corresponding to the built-in implementation of go.

[seankhliao]

Duplicate of #32333

[markusheukelom]

@wizardishungry I'm not completely sure I understand your suggestion, but if mean to say "just write a wrapper function": this is indeed easy. But the problem is that you cannot require its usage and so code that you don't have control over (or did not review throughly) can still easily crash an entire program. I think this is also described in the linked duplicate issue.

We run a "modular monolith" which works really great, except that every once in a while I (or team members) for get to do a defer+recover in a function that is invoke as go-routine. The modules would be better encapsulated if uncaught panic in one go-routine did not crash all other "modules" (ie. the program).

[wizardishungry]

Right – What I'm suggesting is that you be able to register a global wrapper function.

[rsc]

This proposal is a duplicate of a previously discussed proposal, as noted above,
and there is no significant new information to justify reopening the discussion.
The issue has therefore been declined as a duplicate.
— rsc for the proposal review group