I am trying to get my current Session in side a getServerSideProps like this:

export async function getServerSideProps(context: any) {
  const session = await getServerSession(authOptions);

  
  return {
    props: { session },
  };
}

and this is my authOptions file.

export const authOptions: NextAuthOptions = {
  providers: [
    CredentialsProvider({
      name: "Credentials",
      id: "credentials",
      credentials: {
        email: { label: "Email", type: "text", placeholder: "jsmith" },
        password: { label: "Password", type: "password" },
      },
      async authorize(credentials) {
        await connectDB();
        const userFound = await User.findOne({
          email: credentials?.email,
        }).select("+password");

        if (!userFound) throw new Error("Ungültige Email");

        const passwordMatch = await bcrypt.compare(
          credentials!.password,
          userFound.password
        );

        if (!passwordMatch) throw new Error("Ungültiges Passwort");
        return userFound;
      },
    }),
  ],
  pages: {
    signIn: "/login",
  },
  session: {
    strategy: "jwt",
  },
  callbacks: {
    async jwt({ token, user, session, trigger }) {
      if (trigger === "update" && session?.name) {
        token.name = session.name;
      }

      if (trigger === "update" && session?.email) {
        token.email = session.email;
      }

      if (user) {
        const u = user as unknown as any;
        return {
          ...token,
          id: u.id,
          name: u.firstName,
          email: u.email,
        };
      }
      return token;
    },
    async session({ session, token }) {
      return {
        ...session,
        user: {
          ...session.user,
          _id: token.id,
          name: token.name,
          email: token.email,
        },
      };
    },
  },
};

Running this leads to these errors "Error: MONGODB_URI must be defined" multiple times. My connectDB file is this:
import mongoose from "mongoose";

const { MONGODB_URI } = process.env;

if (!MONGODB_URI) {
  throw new Error("MONGODB_URI must be defined");
}

export const connectDB = async () => {
  try {
    const { connection } = await mongoose.connect(MONGODB_URI);
    if (connection.readyState === 1) {
      console.log("MongoDB Connected");
      return Promise.resolve(true);
    }
  } catch (error) {
    console.error(error);
    return Promise.reject(error);
  }
};

Why cant it read my MONGODB_UI string?
Or is there a better way to get the session?