I am facing the CORS error for a cloud function I recently deployed even though I have included “Access-Control-Allow-Origin”, “*” in my code.

Here is the code

package controllers

import (
    "encoding/json"
    "fmt"
    "net/http"

    "cloud.google.com/go/firestore"
    "cloud.google.com/go/logging"
    "github.com/Task3/models"
    "github.com/Task3/validations"
)

func CreateEmployee(w http.ResponseWriter, r *http.Request) {

    mu.Lock()
    defer mu.Unlock()

    var employee models.Employee
    err := json.NewDecoder(r.Body).Decode(&employee)

    if err != nil {
        w.Header().Set("Content-Type", "text/plain")
        http.Error(w, "Invalid JSON", http.StatusBadRequest)

        logger.Log(logging.Entry{
            Payload:  "Invalid JSON input for type Employee during controllers.CreateEmployee function call.",
            Severity: logging.Error,
        })
        w.Header().Set("Content-Type", "application/json")
        return
    }

    err1 := validations.V.Struct(employee)

    if err1 != nil {
        w.Header().Set("Content-Type", "text/plain")
        http.Error(w, "Invalid input for employee deatails\n-First name must contain alphabets or spaces only.\n-First name must contain alphabets or spaces only.\n-Email id must be valid eg. abc@example.com.\n-Password must be atleast 6 charecters long.\n-Phone no. should be valid.\n-Role must be either of - 'admin', 'developer', 'manager', 'tester'. (case sensetive)\n-Salary must be a number.\n-Birthdate should be in yyyy-mm-dd format.", http.StatusUnprocessableEntity)

        logger.Log(logging.Entry{
            Payload:  fmt.Sprintf("Invalid employee data input : occured while validating employee fields during controllers.CreateEmployee function call.\n%v", err1),
            Severity: logging.Error,
        })

        w.Header().Set("Content-Type", "application/json")
        return
    }

    // Query to get the maximum employee ID
    iter := client.Collection("ems").OrderBy("ID", firestore.Desc).Limit(1).Documents(ctx)

    var lastEmployee models.Employee

    for {
        doc, err := iter.Next()
        if err != nil {
            break
        }
        doc.DataTo(&lastEmployee)
        // break
    }

    // Generate new employee ID
    EmpId := lastEmployee.ID + 1
    employee.ID = EmpId

    // Save employee data to Firestore
    _, _, err = client.Collection("ems").Add(ctx, employee)
    if err != nil {
        logger.Log(logging.Entry{
            Payload:  "Failed to create employee",
            Severity: logging.Error,
        })
        w.Header().Set("Content-Type", "text/plain")
        http.Error(w, "Failed to create employee", http.StatusInternalServerError)
        return
    }

    // Setting headers and staus codes
    // Set CORS headers for all requests
    w.Header().Set("Access-Control-Allow-Origin", "*")
    w.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS")
    w.Header().Set("Access-Control-Allow-Headers", "Content-Type")

    // Handle preflight request
    if r.Method == http.MethodOptions {
        w.WriteHeader(http.StatusNoContent)
        return
    }

    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusCreated)
    json.NewEncoder(w).Encode(employee)

    logger.Log(logging.Entry{
        Payload:  fmt.Sprintf("Employee created successfully with emp id %v", EmpId),
        Severity: logging.Info,
    })

}

It works on postman but not on other clients than postman. Please suggest something…

I deployed my cloud function by adding appropriate headers for CORS but its still give me a CORS failure error whenever I try to invoke my function.