add: new input scanning exercises

23-input-scanning/exercises/04-grep/solution/main.go

@@ -0,0 +1,31 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func main() {
+	in := bufio.NewScanner(os.Stdin)
+
+	var pattern string
+	if args := os.Args[1:]; len(args) == 1 {
+		pattern = args[0]
+	}
+
+	for in.Scan() {
+		s := in.Text()
+		if strings.Contains(s, pattern) {
+			fmt.Println(s)
+		}
+	}
+}

23-input-scanning/exercises/04-grep/solution/shakespeare.txt

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+come night come romeo come thou day in night
+for thou wilt lie upon the wings of night
+whiter than new snow on a raven's back
+come gentle night come loving black-browed night
+give me my romeo and when he shall die
+take him and cut him out in little stars
+and he will make the face of heaven so fine
+that all the world will be in love with night
+and pay no worship to the garish sun
+oh i have bought the mansion of love
+but not possessed it and though i am sold
+not yet enjoyed