Swift Variable not Changing - swift

Question

Below is my function which is not changing the return Value. How do I get the function to return the modified returnVal?
func RecieveActivitySummary() -> HKActivitySummary {
var returnVal = HKActivitySummary()
self.makeQuery() { (summary) in
returnVal = summary //attempting to alter returnVal
print(returnVal) //prints out returnVal object that I want with data (seemingly modified)
}
print(returnVal) //prints out unmodified returnVal
return returnVal //then goes on to return an empty returnVal object
}
Here is my makeQuery() function if it helps address the problem:
func makeQuery(completion: #escaping (_ summary : HKActivitySummary) -> ()) {
let calendar = NSCalendar.current
let endDate = Date()
guard let startDate = calendar.date(byAdding: .day, value: 0, to: endDate) else {
fatalError("error")
}
let units: Set<Calendar.Component> = [.day, .month, .year, .era]
var startDatecomps = calendar.dateComponents(units, from: startDate)
startDatecomps.calendar = calendar
var endDatecomps = calendar.dateComponents(units, from: endDate)
endDatecomps.calendar = calendar
let summariesWithinRange = HKQuery.predicate(forActivitySummariesBetweenStart: startDatecomps, end: endDatecomps)
let query = HKActivitySummaryQuery(predicate: summariesWithinRange) {
(sample, results, error) -> Void in
if let results = results {
var summary = results[0]
completion(summary)
}
}
healthstore.execute(query)
}