locktime – send btc from P2SH(multisig and timelock script),got “Non-canonical DER signature”

I created a 2/3 multisig script with timelock,the admin can withdraw BTC after timelock.
But the bitcoin node return an error:code:-26,message:mandatory-script-verify-flag-failed (Non-canonical DER signature).

func createMultisigLocktimeRedeemScript(pk1, pk2, pk3, pkAdmin []byte, locktime uint32) ([]byte, error) {
builder := txscript.NewScriptBuilder()

builder.AddOp(txscript.OP_IF)
// multisig
{
    // add the minimum number of needed signatures
    builder.AddOp(txscript.OP_2)
    builder.AddData(pk1)
    builder.AddData(pk2)
    builder.AddData(pk3)
    // add the total number of public keys in the multi-sig screipt
    builder.AddOp(txscript.OP_3)
    // add the check-multi-sig op-code
    builder.AddOp(txscript.OP_CHECKMULTISIG)
}

builder.AddOp(txscript.OP_ELSE)
// locktime
{
    var bz = make([]byte, 4)
    binary.LittleEndian.PutUint32(bz, locktime) //
    builder.AddData(bz)
    builder.AddOp(txscript.OP_CHECKLOCKTIMEVERIFY)
    builder.AddOp(txscript.OP_DROP)
}
builder.AddOp(txscript.OP_ENDIF)

// admin
{
    builder.AddData(pkAdmin)
    builder.AddOp(txscript.OP_CHECKSIG)
}

// redeem script is the script program in the format of []byte
redeemScript, err := builder.Script()
if err != nil {
    return nil, err
}
redeemStr, err := txscript.DisasmString(redeemScript)
if err != nil {
    return nil, err
}
fmt.Println("script:", redeemStr)

{
    redeemHash := btcutil.Hash160(redeemScript)
    scriptAddr, err := btcutil.NewAddressScriptHashFromHash(redeemHash, &chaincfg.TestNet3Params) //P2SH
    if err != nil {
        return nil, err
    }
    fmt.Printf("network %s script address: %s\n", "testnet3", scriptAddr.EncodeAddress())
}
return redeemScript, nil

}

func multisigLockTimeTx(sk1, sk2, sk3, skAdmin string, locktime uint32) error {
wif1, err := btcutil.DecodeWIF(sk1)
if err != nil {
    return err
}
pk1 := wif1.PrivKey.PubKey().SerializeCompressed()

wif2, err := btcutil.DecodeWIF(sk2)
if err != nil {
    return err
}
pk2 := wif2.PrivKey.PubKey().SerializeCompressed()

wif3, err := btcutil.DecodeWIF(sk3)
if err != nil {
    return err
}
pk3 := wif3.PrivKey.PubKey().SerializeCompressed()

wifAdmin, err := btcutil.DecodeWIF(skAdmin)
if err != nil {
    return err
}
pkAdmin := wifAdmin.PrivKey.PubKey().SerializeCompressed()

redeemScript, err := createMultisigLocktimeRedeemScript(pk1, pk2, pk3, pkAdmin, locktime)
if err != nil {
    return err
}

// build tx
redeemTx := wire.NewMsgTx(wire.TxVersion)

// you should provide your UTXO hash
utxoHash, err := chainhash.NewHashFromStr("deabddd6f7ebed78fe91b71a34ec7167360a49016be039fd2b053ac02388e449")
if err != nil {
    return nil
}
// and add the index of the UTXO
outPoint := wire.NewOutPoint(utxoHash, 0)
txIn := wire.NewTxIn(outPoint, nil, nil)

redeemTx.AddTxIn(txIn)

// adding the output to tx
decodedAddr, err := btcutil.DecodeAddress("tb1ph8jzyv68rwx436wtnr760tsg3ut07ml8zueuqcwww04fdmrp8ntqaqjmsp", &chaincfg.TestNet3Params)
if err != nil {
    return err
}
destinationAddrByte, err := txscript.PayToAddrScript(decodedAddr)
if err != nil {
    return err
}
// adding the destination address and the amount to the transaction
redeemTxOut := wire.NewTxOut(5000, destinationAddrByte)
redeemTx.AddTxOut(redeemTxOut)

sig1, err := txscript.RawTxInSignature(redeemTx, 0, redeemScript, txscript.SigHashAll, wif1.PrivKey)
if err != nil {
    return err
}
_ = sig1
sig2, err := txscript.RawTxInSignature(redeemTx, 0, redeemScript, txscript.SigHashAll, wif2.PrivKey)
if err != nil {
    return err
}
_ = sig2

sig3, err := txscript.RawTxInSignature(redeemTx, 0, redeemScript, txscript.SigHashAll, wif3.PrivKey)
if err != nil {
    fmt.Println("got error in constructing sig3")
    return err
}
_ = sig3

sigAdmin, err := txscript.RawTxInSignature(redeemTx, 0, redeemScript, txscript.SigHashAll, wifAdmin.PrivKey)
if err != nil {
    fmt.Println("got error in constructing sigAdmin")
    return err
}
_ = sigAdmin

fmt.Println("sig1:", hex.EncodeToString(sig1))
fmt.Println("sig2:", hex.EncodeToString(sig2))
fmt.Println("sig3:", hex.EncodeToString(sig3))
fmt.Println("sigAdmin:", hex.EncodeToString(sigAdmin))

if !isValidSignatur(sig1) {
    fmt.Println("signature invalid")
}
if !isValidSignatur(sig2) {
    fmt.Println("signature invalid")
}
if !isValidSignatur(sig3) {
    fmt.Println("signature invalid")
}
if !isValidSignatur(sigAdmin) {
    fmt.Println("signature invalid")
}

signature := txscript.NewScriptBuilder()
// multisig
{
    signature.AddOp(txscript.OP_0)
    signature.AddData(sig2)
    signature.AddData(sig3)
    signature.AddOp(txscript.OP_TRUE)
    signature.AddData(redeemScript)
}
{ // admin
    //signature.AddData(sigAdmin)
    //signature.AddOp(txscript.OP_FALSE)
    //signature.AddData(redeemScript)
}
signatureScript, err := signature.Script()
if err != nil {
    // Handle the error.
    return err
}

signatureScriptStr, err := txscript.DisasmString(signatureScript)
if err != nil {
    return err
}
fmt.Println("signatureScript:", signatureScriptStr)

redeemTx.TxIn[0].SignatureScript = signatureScript
var signedTx bytes.Buffer
if err := redeemTx.Serialize(&signedTx); err != nil {
    return err
}
fmt.Println("TxHash:", redeemTx.TxHash().String())

hexSignedTx := hex.EncodeToString(signedTx.Bytes())
fmt.Println("signedTx:", hexSignedTx)

var multi_expporer_api = []string{"https://blockstream.info/testnet/api/"}
cli := bitcoinlib.NewSmartClient(multi_expporer_api)
txid, err := cli.PostTransaction(context.Background(), hexSignedTx)
if err != nil {
    return err
}
fmt.Println("txid:", txid)
return nil

}

script:

OP_IF
  2
  03f5d066de8a9d8476f8eab2f507f2858ef0914ccf96bf3752f3f4652553c52b6d
  023fe85a4a866ef5f4af2d1904e1ac3bec518542b13837ae1159d707650796bbe5
  022205cdcd869d9dbec279dadceeef7777e39d1915e2f36ec0f6e3fa50bb024c5c
  3
  OP_CHECKMULTISIG
OP_ELSE
  900c1a67
  OP_CHECKLOCKTIMEVERIFY
  OP_DROP
OP_ENDIF
035d911aded72d77f12e5d200d37f968438c6c7d532b2dbf50a80516ab1014e52b
OP_CHECKSIG

network testnet3 script address: 2MsWVE37DGR7adHWiZpUh7va71qkX26Vbp8

sig1: 3044022017a98dfea76746e9b7f0f785c7d92625289b0b0b5b95b47072511c24f5f3769302201033ff85eec8ce951100c3f6459a439bdb13e24acd7d59609bc2b76a7b24503c01

sig2: 3045022100fc71b478e03ce44c8148bfd19a69175ce744d15f822851ca18d4c95cca08dcec02202dd451b493e8ffe64fb672a9740b49af95cb731a60fc386612983304f656681901

sig3: 3045022100f815e290b3c83160f49b56b9c18b0834f25f1752883ae83399cdfc34646a0cdb022051a687e58f88ebac3dd0430be22d9b0e1270bcd25e19732baf612ecd113da86801

sigAdmin: 3045022100a85f88f394cabcf2659fa62f98ca56b26be5f7c4f9645c2922f6e52d01ef527d02207075c8af70d358f04b6fb1dfc0c19faaa274577ccc68f411370fbbae60aee79101

signatureScript: 0 3045022100fc71b478e03ce44c8148bfd19a69175ce744d15f822851ca18d4c95cca08dcec02202dd451b493e8ffe64fb672a9740b49af95cb731a60fc386612983304f656681901 3045022100f815e290b3c83160f49b56b9c18b0834f25f1752883ae83399cdfc34646a0cdb022051a687e58f88ebac3dd0430be22d9b0e1270bcd25e19732baf612ecd113da86801 1 63522103f5d066de8a9d8476f8eab2f507f2858ef0914ccf96bf3752f3f4652553c52b6d21023fe85a4a866ef5f4af2d1904e1ac3bec518542b13837ae1159d707650796bbe521022205cdcd869d9dbec279dadceeef7777e39d1915e2f36ec0f6e3fa50bb024c5c53ae6704900c1a67b1756821035d911aded72d77f12e5d200d37f968438c6c7d532b2dbf50a80516ab1014e52bac

TxHash: 03386f8a777ae44b2ee6ab4d494b46a55655fa7825c04dd9b7cf993086976669

signedTx: 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