added gocat implementation

src/gocat/main.go

+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+const BUFFERSIZE = 1024
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: gocat [file ...]")
+	}
+	files := os.Args[1:]
+	for _, file := range files {
+		if err := processFile(file); err != nil {
+			fmt.Fprintf(os.Stderr, "gocat: %v", err)
+		}
+	}
+}
+
+func processFile(filename string) error {
+	var f *os.File
+	if filename == "-" {
+		f = os.Stdin
+	} else {
+		var err error
+		// f, err := doesn't work as this would keep the f scope local
+		f, err = os.Open(filename)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+	}
+	if err := bufferedCopy(f, os.Stdout); err != nil {
+		return err
+	}
+	return nil
+}
+
+func bufferedCopy(source io.Reader, destination io.Writer) error {
+	buf := make([]byte, BUFFERSIZE)
+	for {
+		n, err := source.Read(buf)
+		if err != nil && err != io.EOF {
+			return err
+		}
+		if n == 0 {
+			break
+		}
+
+		if _, err := destination.Write(buf[:n]); err != nil {
+			return err
+		}
+	}
+	return nil
+}