Add parsing rules, and a test case, for "Go panicing in a http handler". (#49)

Author: vatine

.rubocop.yml

@@ -26,7 +26,7 @@ Metrics/CyclomaticComplexity:
 # Offense count: 5
 # Configuration parameters: CountComments.
 Metrics/MethodLength:
-  Max: 150
+  Max: 160
 
 # Offense count: 3
 Metrics/PerceivedComplexity:

lib/fluent/plugin/exception_detector.rb

@@ -83,6 +83,8 @@ def self.supported
 
     GO_RULES = [
       rule(:start_state, /\bpanic: /, :go_after_panic),
+      rule(:start_state, /http: panic serving/, :go_goroutine),
+      rule(:go_after_panic, /^$/, :go_goroutine),
       rule([:go_after_panic, :go_after_signal, :go_frame_1],
            /^$/, :go_goroutine),
       rule(:go_after_panic, /^\[signal /, :go_after_signal),

test/plugin/test_exception_detector.rb

@@ -242,6 +242,26 @@ class ExceptionDetectorTest < Test::Unit::TestCase
 	server.go:20 +0x91
 END
 
+  GO_HTTP = <<END.freeze
+2019/01/15 07:48:05 http: panic serving [::1]:54143: test panic
+goroutine 24 [running]:
+net/http.(*conn).serve.func1(0xc00007eaa0)
+	/usr/local/go/src/net/http/server.go:1746 +0xd0
+panic(0x12472a0, 0x12ece10)
+	/usr/local/go/src/runtime/panic.go:513 +0x1b9
+main.doPanic(0x12f0ea0, 0xc00010e1c0, 0xc000104400)
+	/Users/ingvar/src/go/src/httppanic.go:8 +0x39
+net/http.HandlerFunc.ServeHTTP(0x12be2e8, 0x12f0ea0, 0xc00010e1c0, 0xc000104400)
+	/usr/local/go/src/net/http/server.go:1964 +0x44
+net/http.(*ServeMux).ServeHTTP(0x14a17a0, 0x12f0ea0, 0xc00010e1c0, 0xc000104400)
+	/usr/local/go/src/net/http/server.go:2361 +0x127
+net/http.serverHandler.ServeHTTP(0xc000085040, 0x12f0ea0, 0xc00010e1c0, 0xc000104400)
+	/usr/local/go/src/net/http/server.go:2741 +0xab
+net/http.(*conn).serve(0xc00007eaa0, 0x12f10a0, 0xc00008a780)
+	/usr/local/go/src/net/http/server.go:1847 +0x646
+created by net/http.(*Server).Serve
+	/usr/local/go/src/net/http/server.go:2851 +0x2f5
+END
   CSHARP_EXC = <<END.freeze
 System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2[System.String,System.Collections.Generic.Dictionary`2[System.Int32,System.Double]].get_Item (System.String key) [0x00000] in <filename unknown>:0
@@ -585,6 +605,7 @@ def test_go
     check_exception(GO_EXC, false)
     check_exception(GO_ON_GAE_EXC, false)
     check_exception(GO_SIGNAL_EXC, false)
+    check_exception(GO_HTTP, false)
   end
 
   def test_ruby