[CI] Fix the issue of unit test hanging (#1211)

test/srt/run_suite.py

@@ -1,5 +1,6 @@
 import argparse
 import glob
+import multiprocessing as mp
 
 from sglang.test.test_utils import run_unittest_files
 
@@ -54,5 +55,10 @@ if __name__ == "__main__":
     else:
         files = suites[args.suite]
 
+    try:
+        mp.set_start_method("spawn")
+    except RuntimeError:
+        pass
+
     exit_code = run_unittest_files(files, args.timeout_per_file)
     exit(exit_code)