Calculate the limit
$$\lim_{n \to \infty} \frac{1}{n} \left(\frac{1}{n^k} +\frac{2^k}{n^k} +....+\frac{(n-1)^k}{n^k} +\frac{n^k}{n^k}\right).$$
(For the calculation of the limit, the integral construction procedure can be followed).
To solve the given limit, we will use the concept of the Riemann sum to convert the sum into an integral. The given limit is:

$$ \lim_{n \to \infty} \frac{1}{n} \left(\frac{1}{n^k} +\frac{2^k}{n^k} + \cdots +\frac{(n-1)^k}{n^k} +\frac{n^k}{n^k}\right). $$

1. **Rewrite the sum in a more convenient form:**

   The expression inside the limit can be rewritten as:
   $$ \frac{1}{n} \sum_{i=1}^{n} \frac{i^k}{n^k}. $$

2. **Simplify the sum:**

   Factor out the common term \( \frac{1}{n^{k+1}} \):
   $$ \frac{1}{n^{k+1}} \sum_{i=1}^{n} i^k. $$

3. **Recognize the Riemann sum:**

   Notice that the sum \( \sum_{i=1}^{n} i^k \) can be interpreted as a Riemann sum for the function \( f(x) = x^k \) over the interval \([0, 1]\). Specifically, we have:
   $$ \sum_{i=1}^{n} \left( \frac{i}{n} \right)^k \cdot \frac{1}{n}. $$

4. **Convert the sum to an integral:**

   As \( n \to \infty \), the Riemann sum converges to the integral:
   $$ \int_{0}^{1} x^k \, dx. $$

5. **Evaluate the integral:**

   The integral of \( x^k \) from 0 to 1 is:
   $$ \int_{0}^{1} x^k \, dx = \left[ \frac{x^{k+1}}{k+1} \right]_{0}^{1} = \frac{1}{k+1}. $$

6. **Combine the results:**

   Therefore, the limit can be written as:
   $$ \lim_{n \to \infty} \frac{1}{n^{k+1}} \sum_{i=1}^{n} i^k = \frac{1}{k+1}. $$

Conclusion:
The limit evaluates to \( \frac{1}{k+1} \).

The final answer is \( \boxed{\frac{1}{k+1}} \).