First start with a new config dir, ^C after a while, fails to shutdown:
jb@kvin:~ % STTRACE=app syncthing -home tmp/asdasdasd
[monitor] 2020/02/04 08:25:20.163238 utils.go:56: INFO: Default folder created and/or linked to new config
[start] 2020/02/04 08:25:20.180246 main.go:544: INFO: syncthing v1.3.4-rc.1+17-g9de8602d5-dedupblocklist "Fermium Flea" (go1.13.3 darwin-amd64) jb@kvin.kastelo.net 2020-01-22 07:27:01 UTC
[start] 2020/02/04 08:25:20.180353 utils.go:33: INFO: Generating ECDSA key and certificate for syncthing...
...
[WJIUS] 2020/02/04 08:25:21.722312 syncthing.go:332: INFO: My name is "kvin.kastelo.net"
^C[monitor] 2020/02/04 08:25:25.286605 monitor.go:153: INFO: Signal 2 received; exiting
[WJIUS] 2020/02/04 08:25:25.286687 relay_listen.go:121: INFO: Relay listener (dynamic+https://relays.syncthing.net/endpoint) shutting down
[WJIUS] 2020/02/04 08:25:25.666244 tcp_listen.go:87: INFO: TCP listener ([::]:22000) shutting down
[WJIUS] 2020/02/04 08:25:32.673225 service.go:67: INFO: Detected 1 NAT service
[WJIUS] 2020/02/04 08:25:42.676447 syncthing.go:369: WARNING: Database failed to stop within 10s
[WJIUS] 2020/02/04 08:25:42.676460 syncthing.go:372: INFO: Exiting
jb@kvin:~ %