Splunk regex ignore fields before match

[leandromatperei]

I need to extract the contents of the message field, but the first strings must be ignored, I need to get from the stdout field.
Any ideas how to do this?

Examples:

message: 2021-12-02T20:06:11.541111542Z stdout F 2021-12-02 17:06:11,540 Completed 200 OK

message: 2021-12-02T20:06:11.540863953Z stdout F     contract: txt (truncated)...]

message: 2021-12-02T20:06:11.540857713Z stdout F     clientDocument: txt

[ITWhisperer]

| rex "message:.+stdout (?<stdout>.+)"