diff --git a/interfaces/12-marshaler/main.go b/interfaces/12-marshaler/main.go
index 94bf5a7..1af8345 100644
--- a/interfaces/12-marshaler/main.go
+++ b/interfaces/12-marshaler/main.go
@@ -17,14 +17,14 @@ func main() {
 	// First encode products as JSON:
 	data, err := encode()
 	if err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 	fmt.Println(string(data))
 
 	// Then decode them back from JSON:
 	l, err := decode(data)
 	if err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 
 	// Let the list value print itself:
@@ -46,7 +46,7 @@ Summary:
   - There are several other functions in the strconv package for other primitive types as well.
   - Do not make unnecessary string <-> []byte conversions.
 
-- log.Fatalln() can print the given error message and terminate the program.
+- log.Fatal() can print the given error message and terminate the program.
   - Use it only from the main(). Do not use it in other functions.
   - main() is should be the main driver of a program.
 */
diff --git a/interfaces/13-io/main.go b/interfaces/13-io/main.go
index ac638ff..1cf2cd8 100644
--- a/interfaces/13-io/main.go
+++ b/interfaces/13-io/main.go
@@ -21,31 +21,31 @@ func main() {
 	// #1: reads from the standard input
 	// ------------------------------------------------
 	// if err := read(os.Stdin); err != nil {
-	// 	log.Fatalln(err)
+	// 	log.Fatal(err)
 	// }
 
 	// #2: writes to the standard output
 	// ------------------------------------------------
 	// buf := []byte("hi!\n")
 	// if err := write(os.Stdout, buf); err != nil {
-	// 	log.Fatalln(err)
+	// 	log.Fatal(err)
 	// }
 
 	// #2b: reads the entire file content into memory.
 	// ------------------------------------------------
 	// buf, err := ioutil.ReadFile("alice.txt")
 	// if err != nil {
-	// 	log.Fatalln(err)
+	// 	log.Fatal(err)
 	// }
 	// if err := write(os.Stdout, buf); err != nil {
-	// 	log.Fatalln(err)
+	// 	log.Fatal(err)
 	// }
 
 	// #3: reads and writes with 32KB of memory
 	//     no matter how large the source data is.
 	// ------------------------------------------------
 	if err := ioCopy(os.Stdout, os.Stdin); err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 }
 
diff --git a/logparser/v5/main.go b/logparser/v5/main.go
index 167fc28..b644213 100644
--- a/logparser/v5/main.go
+++ b/logparser/v5/main.go
@@ -22,10 +22,10 @@ func main() {
 
 	p, err := fromFile(os.Args[1])
 	if err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 
 	if err := p.Run(); err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 }
diff --git a/logparser/v6/main.go b/logparser/v6/main.go
index e4f2ef9..ae1c5fd 100644
--- a/logparser/v6/main.go
+++ b/logparser/v6/main.go
@@ -27,10 +27,10 @@ func main() {
 		g.Group(p.Value())
 	}
 	if err := p.Err(); err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 
 	if err := report.Text(os.Stdout, g.Records()); err != nil {
-		log.Fatalln(err)
+		log.Fatal(err)
 	}
 }