idp example: failed to validate request: EOF

[aep]

this is likely user error, as i'm totally new to saml.

1. saml/example/idp/idp -idp https://example.com/
2. go to https://samltest.id/upload.php and fetch https://example.com/metadata
3. download https://samltest.id/saml/providers and curl -X PUT https://example.com/services/what -d '@samltestid.xml'
4. start a flow from https://samltest.id/start-idp-test/
5. the login form shows fine, but when the form posts, with or without correct credentials:
6. bad request: failed to validate request: EOF

i noticed that in the form that is rendered, there's a hidden field, but its empty

<input type="hidden" name="SAMLRequest" value="" /><input type="hidden" name="RelayState" value="" />

2023/03/19 20:42:35.903340 Starting Goji on [::]:16667
2023/03/19 20:43:27.503248 [whale/6BUsY31YzP-000005] Started GET "/metadata" from 10.128.9.1:59994
2023/03/19 20:43:27.503641 [whale/6BUsY31YzP-000005] Returning 200 in 342.918µs
2023/03/19 20:47:30.507802 [whale/6BUsY31YzP-000013] Started PUT "/services/what" from 10.128.9.1:34520
2023/03/19 20:47:30.544169 [whale/6BUsY31YzP-000013] Returning 204 in 36.338998ms
2023/03/19 20:47:40.247274 [whale/6BUsY31YzP-000014] Started GET "/sso?SAMLRequest=fZFfT4MwFMW%2FCun7KP%2FGpBkkuD24ZCoZ6IMvpms7aYQWe8vUby8MjTMxe2vSc3%2FnnnOXQNumI3lva7UTb70A63y0jQJy%2BkhRbxTRFCQQRVsBxDJS5rdbErge6Yy2mukGOTmAMFZqtdIK%2BlaYUpijZOJht01RbW0HBOORaAcDV3Jc1nK%2F142wtQug8YgMcHFfVshZDxKp6Ej7neXiOKOic18N7TlrdM9dptuBCRo5m3WKnimPuDdfRFdhfGDBwedeFCcsYfMkjMKYx4MMoBcbBZYqm6LAC8KZF878pPITEi1I5D0hp%2FiOdC0Vl%2Brlcv79JAJyU1XFbNr%2BURg4bT4IULYcM5OTsTnr9TKW%2FpSJsv%2BqG98YuiU%2BY09GHbkbYJt1oRvJPp28afT7yghqRYp8hLNp5O%2B1sy8%3D&RelayState=ss%3Amem%3Aea02ffb45ace0028fb9a598f9b02fd0e7dbe5eb8d534e2bb8dc72b1994923787" from 10.128.9.1:35294
2023/03/19 20:47:40.247843 [whale/6BUsY31YzP-000014] Returning 200 in 534.772µs
2023/03/19 20:48:02.691238 [whale/6BUsY31YzP-000015] Started GET "/sso" from 10.128.9.1:35586
2023/03/19 20:48:02 failed to parse request: cannot decompress request: unexpected EOF
2023/03/19 20:48:02.691392 [whale/6BUsY31YzP-000015] Returning 400 in 91.003µs