getstudentinfo.go

package getstudentinfo
//You enter a student id
// You get back the student result
//This is a rewrite of the original API in Delphi
// I am using Fiebirdsql 
import (
"context"
"golang.org/x/sync/singleflight"
"database/sql"
_ "github.com/nakagami/firebirdsql"
)

func main() {
    writeLn("The magic happens here.")
    //Forgive me for mixing Pascal code with Go afterall am using pascal IDE called Element from RemObjects to code
}

type StudentInfoParams struct {
    StudentID string // Matriculation No    
}


type StudentResult struct {
    GPA float32 // Grade point average
    Grade string // "A", "B", "C" etc
}

var group singleflight.Group

// Student info does the magic
// After all this is the public API
func Student(ctx context.Context, params *StudentInfoParams) (*StudentResult, error) {
    res, err, _ := group.Do(params.Name, func() (interface{}, error) {
        stdresult, err := queryDB(ctx, params.Name)
        return stdresult, err
    })
    if err != nil {
        return nil, err
    }
    return res.(*StudentResult), nil
}

func queryDB(ctx context.Context, studentid string) (*StudentResult, error) {
    var stdresult StudentResult
   
    conn, _ := sql.Open("firebirdsql", "user:password@servername/ereSchoolERP.fdb")
    defer conn.Close()
    
    err := conn.QueryRow(ctx, `
        SELECT g.grades, g.gpa
        FROM grades g
        WHERE a.studentid = $1
    `, studentid).Scan(&stdresult.GPA, &stdresult.Grade)
    return &stdresult, err
}