Refactor the code to remove global variables

src/functions.go

@@ -0,0 +1,35 @@
+package fzf
+
+import (
+	"os"
+	"strings"
+	"unsafe"
+)
+
+func writeTemporaryFile(data []string, printSep string) string {
+	f, err := os.CreateTemp("", "fzf-preview-*")
+	if err != nil {
+		// Unable to create temporary file
+		// FIXME: Should we terminate the program?
+		return ""
+	}
+	defer f.Close()
+
+	f.WriteString(strings.Join(data, printSep))
+	f.WriteString(printSep)
+	return f.Name()
+}
+
+func removeFiles(files []string) {
+	for _, filename := range files {
+		os.Remove(filename)
+	}
+}
+
+func stringBytes(data string) []byte {
+	return unsafe.Slice(unsafe.StringData(data), len(data))
+}
+
+func byteString(data []byte) string {
+	return unsafe.String(unsafe.SliceData(data), len(data))
+}