NOT NULL constraint failed: statussaver_post.user_id

I'm trying to save a user post data through a modelform in django. Unfortunately, I stumbled to NOT NULL constraint failed:statussaver_post.user_id. Here's my post model.

class post(models.Model):
     content=models.TextField(null=True,blank=True)

     title = models.CharField(max_length=200,null=True,blank=True)
     vedio = models.FileField(upload_to='vedios', blank=True, null=True)
     img = models.ImageField(upload_to='images', null=True, blank=True)
     created = models.DateTimeField(auto_now_add=True)

     class Meta:
         ordering = ('-created',)

     def __str__(self):
        return self.title

I handle the request in views.py as shown below.

def userpost(request):

    if request.method=='POST':
        form=uploadform(request.POST,request.FILES)
        if form.is_valid():
            form.save()
            return redirect('home')
    else:
        form=uploadform()
    return render(request,'statussaver/u.html',{'form':form,})

The form in the code above is called from forms.py as presented below.

from django import forms
from .models import post

class uploadform(forms.ModelForm):
    class Meta:
        model=post
        fields= '__all__'

What should I do to fix this error ?