replace log.Fatal with cobra.CheckErr

cmd/convergents.go

@@ -18,7 +18,6 @@ package cmd
 
 import (
 	"fmt"
-	"log"
 	"math/big"
 
 	"github.com/spf13/cobra"
@@ -41,14 +40,14 @@ func convergents(cmd *cobra.Command, args []string) {
 
 	a0, ok := new(big.Int).SetString(args[0], 10)
 	if !ok {
-		log.Fatal("invalid input " + args[0])
+		cobra.CheckErr("invalid input " + args[0])
 	}
 
 	denoms := make([]big.Int, len(args[1:]))
 	for i, d := range args[1:] {
 		_, ok = denoms[i].SetString(d, 10)
 		if !ok {
-			log.Fatal("invalid input " + d)
+			cobra.CheckErr("invalid input " + d)
 		}
 	}