Golang: cannot use sql.NamedArg in prepared statement - mysql

Question

I have a query that is using NamedArgs from the sql.DB and I'm getting an error when building
cannot use args (type []sql.NamedArg) as type []interface {} in argument to stmt.Exec
The example in the SQL library shows it being used:
Example usage:
db.ExecContext(ctx, `
delete from Invoice
where
TimeCreated < #end
and TimeCreated >= #start;`,
sql.Named("start", startTime),
sql.Named("end", endTime),
)
The only difference is that I'm currently using a prepared statement stmt and calling the Exec method on that. I've created a slice of NamedArg with my values and it's using the ... expander.
res, err := stmt.Exec(args...)
What exactly is wrong when the example shows the sql.Named() method call directly in the code? Why wouldn't an expanded slice work?

Answer 1

That's just how passing arguments to a variadic function works in Go. You either pass the individual values which can be of any type, or you pass in a slice whose element type matches exactly that of the variadic parameter and follow it with ....
I.e. you can either do:
res, err := stmt.Exec(
sql.Named("start", startTime),
sql.Named("end", endTime),
)
or you can do:
args := []interface{}{
sql.Named("start", startTime),
sql.Named("end", endTime),
}
res, err := stmt.Exec(args...)