You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: dlacn2.go
    path of file: ./repos/hoverfly/vendor/gonum.org/v1/gonum/lapack/gonum
    
    the code of the file until where you have to start completion: // Copyright ©2015 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gonum

import (
	"math"

	"gonum.org/v1/gonum/blas/blas64"
)

// Dlacn2 estimates the 1-norm of a
    
func (impl Implementation) Dlacn2(n int, v, x []float64, isgn []int, est float64, kase int, isave *[3]int) (float64, int) {
	switch {
	case n < 1:
		panic(nLT1)
	case len(v) < n:
		panic(shortV)
	case len(x) < n:
		panic(shortX)
	case len(isgn) < n:
		panic(shortIsgn)
	case isave[0] < 0 || 5 < isave[0]:
		panic(badIsave)
	case isave[0] == 0 && kase != 0:
		panic(badIsave)
	}

	const itmax = 5
	bi := blas64.Implementation()

	if kase == 0 {
		for i := 0; i < n; i++ {
			x[i] = 1 / float64(n)
		}
		kase = 1
		isave[0] = 1
		return est, kase
	}
	switch isave[0] {
	case 1:
		if n == 1 {
			v[0] = x[0]
			est = math.Abs(v[0])
			kase = 0
			return est, kase
		}
		est = bi.Dasum(n, x, 1)
		for i := 0; i < n; i++ {
			x[i] = math.Copysign(1, x[i])
			isgn[i] = int(x[i])
		}
		kase = 2
		isave[0] = 2
		return est, kase
	case 2:
		isave[1] = bi.Idamax(n, x, 1)
		isave[2] = 2
		for i := 0; i < n; i++ {
			x[i] = 0
		}
		x[isave[1]] = 1
		kase = 1
		isave[0] = 3
		return est, kase
	case 3:
		bi.Dcopy(n, x, 1, v, 1)
		estold := est
		est = bi.Dasum(n, v, 1)
		sameSigns := true
		for i := 0; i < n; i++ {
			if int(math.Copysign(1, x[i])) != isgn[i] {
				sameSigns = false
				break
			}
		}
		if !sameSigns && est > estold {
			for i := 0; i < n; i++ {
				x[i] = math.Copysign(1, x[i])
				isgn[i] = int(x[i])
			}
			kase = 2
			isave[0] = 4
			return est, kase
		}
	case 4:
		jlast := isave[1]
		isave[1] = bi.Idamax(n, x, 1)
		if x[jlast] != math.Abs(x[isave[1]]) && isave[2] < itmax {
			isave[2] += 1
			for i := 0; i < n; i++ {
				x[i] = 0
			}
			x[isave[1]] = 1
			kase = 1
			isave[0] = 3
			return est, kase
		}
	case 5:
		tmp := 2 * (bi.Dasum(n, x, 1)) / float64(3*n)
		if tmp > est {
			bi.Dcopy(n, x, 1, v, 1)
			est = tmp
		}
		kase = 0
		return est, kase
	}
	// Iteration complete. Final stage
	altsgn := 1.0
	for i := 0; i < n; i++ {
		x[i] = altsgn * (1 + float64(i)/float64(n-1))
		altsgn *= -1
	}
	kase = 1
	isave[0] = 5
	return est, kase
}