Concurrent map panic in dev server under load

[FelixHeinstadt]

Concurrent map panic in dev server under load

Description

sst dev crashes with a concurrent map access panic when handling many Lambda invocations simultaneously.

Version

SST: 4.1.8

Steps to reproduce

1. Run sst dev
2. Trigger multiple concurrent Lambda invocations
3. Dev server panics and crashes

Stack trace

(sst.log)

goroutine 1186548 [running]:
internal/runtime/maps.fatal({0x10659122b?, 0x0?})
	/opt/hostedtoolcache/go/1.25.7/x64/src/runtime/panic.go:1046 +0x20
github.com/sst/sst/v3/cmd/sst/mosaic/aws.function.func1({0x107e2a3d0, 0x141f41b8c30}, 0x141e83a7b80)
	/home/runner/work/sst/sst/cmd/sst/mosaic/aws/function.go:89 +0x19c
net/http.HandlerFunc.ServeHTTP(...)
net/http.(*ServeMux).ServeHTTP(...)
net/http.serverHandler.ServeHTTP(...)
net/http.(*conn).serve(...)
created by net/http.(*Server).Serve in goroutine 837

AI suggestion: "A sync.RWMutex or sync.Map around the map access in function.go:89 should fix this"

[vimtor]

@FelixHeinstadt are you able to consistently reproduce the issue? i might create a pr for you to test against