Use time.RFC3339Nano instead of time.RFC3339, do not want to loose the millisecond resolution. (#18673)

Author: gonzogomez

modules/openapi-generator/src/main/resources/go/client.mustache

@@ -172,7 +172,7 @@ func parameterAddToHeaderOrQuery(headerOrQueryParams interface{}, keyPrefix stri
 					return
 				}
 				if t, ok := obj.(time.Time); ok {
-					parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefix, t.Format(time.RFC3339), collectionType)
+					parameterAddToHeaderOrQuery(headerOrQueryParams, keyPrefix, t.Format(time.RFC3339Nano), collectionType)
 					return
 				}
 				value = v.Type().String() + " value"