replace log.Fatal with cobra.CheckErr

cmd/jacobi.go

@@ -18,7 +18,6 @@ package cmd
 
 import (
 	"fmt"
-	"log"
 	"math/big"
 
 	"github.com/spf13/cobra"
@@ -30,18 +29,18 @@ var n string
 func jacobi(cmd *cobra.Command, args []string) {
 	x, ok := new(big.Int).SetString(a, 10)
 	if !ok {
-		log.Fatal("invalid input " + a)
+		cobra.CheckErr("invalid input " + a)
 	}
 
 	y, ok := new(big.Int).SetString(n, 10)
 	if !ok {
-		log.Fatal("invalid input " + n)
+		cobra.CheckErr("invalid input " + n)
 	}
 
 	mod := big.NewInt(2)
 	mod.Mod(y, mod)
 	if mod.Cmp(big.NewInt(0)) == 0 {
-		log.Fatal("modulus must be odd")
+		cobra.CheckErr("modulus must be odd")
 	}
 
 	z := big.Jacobi(x, y)