Pass function as argument in Go - function

Question

I've tried to create a function in Go that used to retry any fail query functions (usually because serialization issue).
func retryer(functionA func(interface{}) (interface{}, []error), maxRetry int, waitBetween time.Duration) interface{} {
//when no error in functionA, retryer returns whatever functionA returns
//when maxRetry is reached, returns nil
}
The functions I want to retry are looked like this
func GetTopStudent(classId string) ([]Student, []error) {
//queries top 10 students for class with classId
}
func GetAverageStudentScores(classId string, from time.Time, until time.Time) ([]Pair, []error) {
//queries all average score using aggregate, grouping by studentId
//Pair behaves like C++ pair<string,string>
}
But, the results is a compile error
cannot use GetTopStudent (type func(string) ([]Student, []error)) as type func(interface{}) (interface {}, []error) in argument to retryer
I've tried to modify it a little and I got another compile error
cannot use GetTopStudent (type func(string) ([]Student, []error)) as type func(string) (interface {}, []error) in argument to retryer
Can anyone help me creating a general function to wrap a function to retry on error?

Answer 1

A better way to solve your problem would be to use closures.
For example, change the type of retryer:
func retryer(f func() error, maxRetry int, waitBetween time.Duration) error {
// retry and wait logic
err := f()
// error handling, retry, and wait logic
return err
}
Now call functions to be retried as:
// ...
classId := "some value"
// ...
var st []Student
var errors []error
err := retryer(func() error {
st, errors = GetTopStudent(classId)
// handle errors
return nil
}, numTries, waitTime)
// use st here