add -f flag for passing filename

day-01/internal/two/solve.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"embed"
+	"fmt"
 	"io"
 	"regexp"
 	"slices"
@@ -16,8 +17,11 @@ var files embed.FS
 
 var reNums = regexp.MustCompile(`[0-9]+`)
 
-func Solve() (int, error) {
-	data, _ := files.ReadFile("testdata/input.txt")
+func Solve(filename string) (int, error) {
+	data, err := files.ReadFile(fmt.Sprintf("testdata/%s", filename))
+	if err != nil {
+		return 0, err
+	}
 
 	r := bytes.NewReader(data)
 	left, right, err := parseLines(r)