add chapter 15.7 (#683)

eBook/examples/chapter_15/template_validation.go

@@ -0,0 +1,23 @@
+// template_validation.go
+package main
+
+import (
+	"text/template"
+	"fmt"
+)
+
+func main() {
+	tOk := template.New("ok")
+	//a valid template, so no panic with Must:
+	template.Must(tOk.Parse("/* and a comment */ some static text: {{ .Name }}"))
+	fmt.Println("The first one parsed OK.")
+	fmt.Println("The next one ought to fail.")
+	tErr := template.New("error_template")
+	template.Must(tErr.Parse(" some static text {{ .Name }"))
+}
+
+/* Output:
+The first one parsed OK.
+The next one ought to fail.
+panic: template: error_template:1: unexpected "}" in command
+*/