fix(lexers/go): "~" is a valid token

With the introduction of generics,
tilde is a valid punctuation token in Go programs.
https://go.dev/ref/spec#Operators_and_punctuation

This updates the punctuation regex for the Go lexer,
and adds a test to ensure that it's treated as such.

lexers/go.go

@@ -55,7 +55,7 @@ func goRules() Rules {
 			{`"(\\\\|\\"|[^"])*"`, LiteralString, nil},
 			{`(<<=|>>=|<<|>>|<=|>=|&\^=|&\^|\+=|-=|\*=|/=|%=|&=|\|=|&&|\|\||<-|\+\+|--|==|!=|:=|\.\.\.|[+\-*/%&])`, Operator, nil},
 			{`([a-zA-Z_]\w*)(\s*)(\()`, ByGroups(NameFunction, UsingSelf("root"), Punctuation), nil},
-			{`[|^<>=!()\[\]{}.,;:]`, Punctuation, nil},
+			{`[|^<>=!()\[\]{}.,;:~]`, Punctuation, nil},
 			{`[^\W\d]\w*`, NameOther, nil},
 		},
 	}

lexers/go_test.go

@@ -120,3 +120,29 @@ func TestGoHTMLTemplateNegativeNumber(t *testing.T) {
 		assert.True(t, found)
 	}
 }
+
+func TestGoGenericTokens(t *testing.T) {
+	for _, source := range []string{
+		`type Foo[T any] struct { ~[]T | ~string }`,
+	} {
+		tokens, err := chroma.Tokenise(Go, nil, source)
+		assert.NoError(t, err)
+		assert.Equal(t, source, chroma.Stringify(tokens...))
+
+		// No error tokens.
+		for _, token := range tokens {
+			assert.NotEqual(t, chroma.Error, token.Type,
+				"unexpected error token: %v (%q)", token, token.Value)
+		}
+
+		// "~" must be treated as punctuation.
+		var found bool
+		for _, token := range tokens {
+			if token.Value == "~" {
+				found = true
+				assert.Equal(t, chroma.Punctuation, token.Type)
+			}
+		}
+		assert.True(t, found)
+	}
+}