Update writing-go-programs.md

go/writing-go-programs.md

@@ -45,5 +45,66 @@ $ go install
 
 <h4>Run Program</h4>
 <pre>
-$ $GOPATH/bin/hello
+$ hello
 </pre>
+
+
+<h4>Create package directory</h4>
+<pre>
+$ cd $GOPATH/src/github.com/your_username
+$ mkdir formula
+$ cd formula
+$ nano sqrt.go
+# add to the file: 
+
+package formula
+
+func Sqrt(x float64) float64 {
+	z := 1.0
+	for i := 0; i < 1000; i++ {
+		z -= (z*z - x) / (2 * z)
+	}
+	return z
+}
+
+</pre>
+
+<h4>Build Package</h4>
+<pre>
+$ go build github.com/your_username/formula
+</pre>
+
+<h4>Add Package to existing program</h4>
+<pre>
+package main
+import (
+	"fmt"
+	"github.com/user/newmath"
+)
+func main() {
+	fmt.Printf("Hello, world.  Sqrt(2) = %v\n", newmath.Sqrt(2))
+}
+
+</pre>
+
+<h4>Build Program w/ package dependency</h4>
+<pre>
+$ go install github.com/your_username/hello_world
+</pre>
+
+<h4>Run Program w/ package dependency</h4>
+<pre>
+$ hello
+</pre>
+
+
+
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