Implemented strikethrough text

README.md

@@ -5,7 +5,7 @@ A markdown renderer that supports only a subset of the CommonMark spec in order
 ## Features
 
 - Code blocks
-- Formatting (bold, italic, monospace)
+- Formatting (bold, italic, monospace and strikethrough)
 - Links
 - Lists
 - Headers
@@ -34,6 +34,7 @@ PASS: TestParagraph
 PASS: TestHeader
 PASS: TestItalic
 PASS: TestBold
+PASS: TestStrike
 PASS: TestLink
 PASS: TestList
 PASS: TestTables
@@ -48,9 +49,9 @@ coverage: 100.0% of statements
 ## Benchmarks
 
 ```
-BenchmarkSmall-12        5986922               187.5 ns/op            32 B/op          1 allocs/op
+BenchmarkSmall-12        6202569               190.9 ns/op            32 B/op          1 allocs/op
-BenchmarkMedium-12       1000000              1077 ns/op             512 B/op          1 allocs/op
+BenchmarkMedium-12       1000000              1080 ns/op             512 B/op          1 allocs/op
-BenchmarkLarge-12         255178              4055 ns/op            2560 B/op          2 allocs/op
+BenchmarkLarge-12         271048              4115 ns/op            2560 B/op          2 allocs/op
 ```
 
 ## License

Render.go

@@ -257,11 +257,12 @@ func (r *renderer) writeText(markdown string) {
 		codeStart     = -1
 		emStart       = -1
 		strongStart   = -1
+		strikeStart   = -1
 		parentheses   = 0
 	)
 
 	for {
-		i := strings.IndexAny(markdown[searchStart:], "[]()`*_")
+		i := strings.IndexAny(markdown[searchStart:], "[]()`*_~")
 
 		if i == -1 {
 			r.WriteString(html.EscapeString(markdown[tokenStart:]))
@@ -342,6 +343,23 @@ func (r *renderer) writeText(markdown string) {
 				tokenStart = i
 				emStart = i + 1
 			}
+
+		case '~':
+			if i+1 >= len(markdown) || markdown[i+1] != '~' {
+				continue
+			}
+
+			if strikeStart != -1 {
+				r.WriteString("<del>")
+				r.WriteString(html.EscapeString(markdown[strikeStart:i]))
+				r.WriteString("</del>")
+				strikeStart = -1
+				tokenStart = i + 2
+			} else {
+				r.WriteString(html.EscapeString(markdown[tokenStart:i]))
+				tokenStart = i
+				strikeStart = i + 2
+			}
 		}
 	}
 }

Render_test.go

@@ -39,6 +39,11 @@ func TestBold(t *testing.T) {
 	assert.Equal(t, markdown.Render("__bold__"), "<p><strong>bold</strong></p>")
 }
 
+func TestStrike(t *testing.T) {
+	assert.Equal(t, markdown.Render("~normal text~"), "<p>~normal text~</p>")
+	assert.Equal(t, markdown.Render("~~deleted text~~"), "<p><del>deleted text</del></p>")
+}
+
 func TestLink(t *testing.T) {
 	assert.Equal(t, markdown.Render("[text](https://example.com/)"), "<p><a href=\"https://example.com/\">text</a></p>")
 	assert.Equal(t, markdown.Render("[text](https://example.com/"), "<p>[text](https://example.com/</p>")