How to read extension values like key info and key signature with OID

var cert *x509.Certificate
cert, err := x509.ParseCertificate(myCertificate)

From this I need to retrieve extension values in bytes. I have the OID to be used for that. I am able to find code for adding extensions to a certificate. But not retrieving it. Can anyone share a sample code on how to do that?

Update:

Now, I am able to get the extensions

var extensions []pkix.Extension
var cert *x509.Certificate
byteValue, _ := base64.StdEncoding.DecodeString(myCert)
cert, err := x509.ParseCertificate(byteValue)
if err != nil {
	fmt.Println("Error in parsing certificate")
}
extensions = cert.Extensions
checkId := []int{2, 5, 6, 135, 3, 2, 41}
for _, ext := range extensions {
	if reflect.DeepEqual(ext.Id, checkId) {
		fmt.Println("true")
	}
}

}

But the deep equal return false (the particular oid is present), I need to retrieve the value of that particular extension. Can anyone suggest some steps to do that?

reflect.DeepEqual does not work because the types are different. The normal way to check OIDs is using the asn1.ObjectIdentifier as follows:

checkID := asn1.ObjectIdentifier{2, 5, 6, 135, 3, 2, 41}
for _, ext := range extensions {
    if ext.Id.Equal(checkId) {
        fmt.Println("true")
    }
}

If it isn't there, don't forget to check ExtraExtensions.