Golang Chan is hanging when looping through the results - asynchronous

Question

I am pretty new to GoLang channels, but it isn't working as I would expect.
I have a function that I want to call 3 separate goroutines on and then wait for them all to complete. If I get an error then I am trying to put it on the CHAN and then handle the error after wg.Wait() completes.
Unfortunately, when looping through the CHAN results it will hang. I hypothesize as it is still waiting for the CHAN to get filled but not all goroutines will throw errors.
What is the best way to handle looping through channels that won't always be populated? I also know that I don't have to use CHANs here, but I wanted to make sure that I understood them.
Below is my code.
func createWorkoutPlanForUserPreconditionCheck(planID, userID, transactionID *string) (*sharedstructs.Plan, *sharedstructs.User, *sharedstructs.Profile, error) {
if planID == nil || userID == nil || transactionID == nil {
return nil, nil, nil, sharedstructs.InvalidData{Msg: "Cannot pass in Nil Parameters"}
}
plan := sharedstructs.Plan{}
user := sharedstructs.User{}
profile := sharedstructs.Profile{}
//myError := sharedstructs.InvalidData{}
ch := make(chan sharedstructs.InvalidData, 3)
var wg sync.WaitGroup
wg.Add(3)
//Get the Plan from the Plan ID
go func() {
defer wg.Done()
returnedPlan, readError := readPlan(*planID)
if readError != nil || returnedPlan == nil {
ch <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
plan = *returnedPlan
}
}()
//Get the User
go func() {
defer wg.Done()
returnedUser, getUserError := userdomain.GetUserByID(*userID, *transactionID)
if getUserError != nil || &returnedUser == nil {
ch <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
user = returnedUser
}
}()
//Get the Profile
go func() {
defer wg.Done()
readProfile, getProfileError := profiledomain.GetProfile(*userID, *transactionID)
if getProfileError != nil || readProfile == nil {
ch <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
profile = *readProfile
}
}()
wg.Wait()
////"Hangs Here" - PUT MY ERROR HANDLING LOGIC HERE
for err := range ch {
fmt.Println(err.Error())
}
return &plan, &user, &profile, nil
}

Answer 1

So, not long after posting I figured a solution. My problem was really two fold:
Closing my channel so that it knew when to stop listening
Using inconsistent methods to get my data from my goroutine to my calling function. For errors I was using chan's but for custom structs I was just setting it. I generisized my chan to an interface{} and then did a type switch on it when processing to determine the type of struct that it was.
^^^ fixing these issues made my code work but here is what my code ended up as..
func createWorkoutPlanForUserPreconditionCheck(planID, userID, transactionID *string) (*sharedstructs.Plan, *sharedstructs.User, *sharedstructs.Profile, error) {
if planID == nil || userID == nil || transactionID == nil {
return nil, nil, nil, sharedstructs.InvalidData{Msg: "Cannot pass in Nil Parameters"}
}
outputChannel := make(chan interface{}, 3)
var wg sync.WaitGroup
wg.Add(3)
//Get the Plan from the Plan ID
go func() {
defer wg.Done()
returnedPlan, readError := readPlan(*planID)
if readError != nil || returnedPlan == nil {
outputChannel <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
outputChannel <- *returnedPlan
}
}()
//Get the User
go func() {
defer wg.Done()
returnedUser, getUserError := userdomain.GetUserByID(*userID, *transactionID)
if getUserError != nil || &returnedUser == nil {
outputChannel <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
outputChannel <- returnedUser
}
}()
//Get the Profile
go func() {
defer wg.Done()
readProfile, getProfileError := profiledomain.GetProfile(*userID, *transactionID)
if getProfileError != nil || readProfile == nil {
outputChannel <- sharedstructs.InvalidData{Msg: "Could Not Retreive the User with ID: " + *userID}
} else {
outputChannel <- *readProfile
}
}()
wg.Wait()
close(outputChannel)
plan := sharedstructs.Plan{}
user := sharedstructs.User{}
profile := sharedstructs.Profile{}
for result := range outputChannel {
switch result.(type) {
case sharedstructs.InvalidData:
return nil, nil, nil, result.(sharedstructs.InvalidData)
case sharedstructs.Plan:
plan = result.(sharedstructs.Plan)
case sharedstructs.User:
user = result.(sharedstructs.User)
case sharedstructs.Profile:
profile = result.(sharedstructs.Profile)
}
}
return &plan, &user, &profile, nil
}