import package project

2-importpackage/go.mod

@@ -0,0 +1,3 @@
+module example/user/importpackage
+
+go 1.17

2-importpackage/hello.go

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+package main
+
+import (
+	"fmt"
+
+	"example/user/importpackage/importpackage"
+)
+
+func main() {
+	fmt.Println(importpackage.ReverseRunes("!oG ,olleH"))
+}

2-importpackage/importpackage/reverse.go

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+// Package importpackage implements additional functions to manipulate UTF-8
+// encoded strings, beyond what is provided in the standard "strings" package.
+package importpackage
+
+// ReverseRunes returns its argument string reversed rune-wise left to right.
+func ReverseRunes(s string) string {
+	r := []rune(s)
+	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+	return string(r)
+}

2-importpackage/readme.md

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+# Import package
+write a `importpackage` package and use it from the hello program. 
+
+Because the `ReverseRunes` function begins with an upper-case letter, it is exported and can be used in other packages that import the importpackage package. 
+
+Test that the package compiles with go build:
+```bash
+# init project
+mkdir 2-importpackage
+cd 2-importpackage
+go mod init example/user/importpackage
+# create files
+touch hello.go
+mkdir importpackage
+cd importpackage
+nano reverse.go
+>   // Package importpackage implements additional functions to manipulate UTF-8
+>   // encoded strings, beyond what is provided in the standard "strings" package.
+package importpackage
+>   
+>   // ReverseRunes returns its argument string reversed rune-wise left to right.
+>   func ReverseRunes(s string) string {
+>   	r := []rune(s)
+>   	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+>   		r[i], r[j] = r[j], r[i]
+>   	}
+>   	return string(r)
+>   }
+go build
+```
+
+This won't produce an output file. Instead it saves the compiled package in the local build cache.
+
+After confirming that the importpackage package builds, use it from the `hello` program.
+```bash
+cd ..
+nano hello.go
+>   package main
+>   
+>   import (
+>   	"fmt"
+>   
+>   	"example/user/importpackage/importpackage"
+>   )
+>   
+>   func main() {
+>   	fmt.Println(importpackage.ReverseRunes("!oG ,olleH"))
+>   }
+go run hello.go
+```