添加1.2节的代码

src/1.2/main.go

@@ -0,0 +1,13 @@
+// 章节 1.2
+// $GOPATH/src/mathapp/main.go
+
+package main
+
+import (
+	"fmt"
+	"mymath"
+)
+
+func main() {
+	fmt.Printf("Hello, world.  Sqrt(2) = %v\n", mymath.Sqrt(2))
+}